Orbit 17 +++ Space and beyond
galaxies, science, exploration, astronomy (blog)
Posts tagged Milky Way
Milky Way enigma: Why galaxy’s central black hole is silent
Jan 9th
An image released by NASA Tuesday, shows Sagittarius A, the supermassive black hole at the center of the Milky Way Galaxy made from data provided by the Chandra X-ray Observatory. Credit: NASA/AP
One of the Milky Way’s longstanding puzzles centers on the super-massive black hole at its core, in the constellation Sagittarius: Why is that monstrous black hole, known as Sag A*, so much less energetic that its counterparts in other galaxies?
The behemoth, with some 2.6 million times the sun’s mass, is a cosmic dud at the moment. Something is starving it, depriving it of material that otherwise would plummet into it.
Roman Shcherbakov, a researcher at the Harvard-Smithsonian Center for Astrophysics, says he’s figured out what that “something” is likely to be: heat.
As material from surrounding stars approaches the black hole and gets compressed by the monster’s gravity, it heats up. Some of that heat gets conducted away from the black hole, setting up a source of pressure that sweeps material away from the voracious object.
In other words, heating around the black hole’s event horizon – essentially the boundary within which material falls into oblivion – is in effect starving the black hole.
Voyager 2 on a ‘magic mission’ into Milky Way, or Melkweg in Dutch :)
Dec 30th
A map of the Milky Way. Credit: NASA/JPL
Holiday tidings come from NASA’s Voyager 2 this week, offering a view of deep space beyond our sun’s solar system.
Now speeding through space at more than 34,000 miles-per-hour, the 1977 space probe resides more than 8.3. billion miles away from the sun. That is twice as far as Pluto. Two years ago, Voyager 2 passed into the region of space where the sun’s solar wind peters out as it plows into the interstellar gases of our Milky Way galaxy. And now it’s giving us some news from this region, called the “heliosheath,” by astrophysicists.
“This is a magic mission,” says space scientist Merav Opher of George Mason University. in Fairfax, Va.. “After all these years, Voyager 2 is still working and sending us first hand (on-site) data.”